Merge pull request #477 from scratchcpp/promise_api

Add promise API to VirtualMachine

Author: adazem009

include/scratchcpp/virtualmachine.h

@@ -71,16 +71,16 @@ enum Opcode
     OP_LIST_LENGTH,    /*!< Stores the length of the list with the index in the argument, in the last register. */
     OP_LIST_CONTAINS,  /*!< Stores true in the last register if the list with the index in the argument contains the value from the last register. */
     OP_STR_CONCAT,     /*!< Concatenates the strings stored in the last 2 registers and stores the result in the last register, deleting the input registers. */
-    OP_STR_AT,         /*! Stores the character at index in the last register of the string in the second last register, in the last register. */
-    OP_STR_LENGTH,     /*! Stores the length of the string in the last register, in the last register. */
-    OP_STR_CONTAINS,   /*! Stores true in the last register if the string stored in the second last register contains the substring in the last register. */
+    OP_STR_AT,         /*!< Stores the character at index in the last register of the string in the second last register, in the last register. */
+    OP_STR_LENGTH,     /*!< Stores the length of the string in the last register, in the last register. */
+    OP_STR_CONTAINS,   /*!< Stores true in the last register if the string stored in the second last register contains the substring in the last register. */
     OP_EXEC,           /*!< Calls the function with the index in the argument. */
     OP_INIT_PROCEDURE, /*!< Initializes the list of procedure (custom block) arguments. */
     OP_CALL_PROCEDURE, /*! Calls the procedure (custom block) with the index in the argument. */
     OP_ADD_ARG,        /*!< Adds a procedure (custom block) argument with the value from the last register. */
     OP_READ_ARG,       /*!< Reads the procedure (custom block) argument with the index in the argument and stores the value in the last register. */
     OP_BREAK_FRAME,    /*!< Breaks current frame at the end of the loop. */
-    OP_WARP            /*! Runs the script without screen refresh. */
+    OP_WARP            /*!< Runs the script without screen refresh. */
 };
 
 }
@@ -133,6 +133,8 @@ class LIBSCRATCHCPP_EXPORT VirtualMachine
         void moveToLastCheckpoint();
 
         void stop(bool savePos = true, bool breakFrame = false, bool goBack = false);
+        void promise();
+        void resolvePromise();
 
         bool atEnd() const;
 

src/engine/virtualmachine.cpp

@@ -166,6 +166,9 @@ void VirtualMachine::run()
 {
     impl->running = true;
 
+    if (impl->promisePending)
+        return;
+
     unsigned int *ret = impl->run(impl->pos);
     assert(ret);
 
@@ -187,6 +190,7 @@ void VirtualMachine::reset()
 {
     impl->pos = impl->bytecode;
     impl->atEnd = false;
+    impl->promisePending = false;
 
     if (!impl->running) // Registers will be freed when the script stops running
         impl->regCount = 0;
@@ -216,6 +220,22 @@ void VirtualMachine::stop(bool savePos, bool breakFrame, bool goBack)
     impl->goBack = goBack;
 }
 
+/*!
+ * Use this to pause the execution of the script.
+ * The execution will continue after calling resolvePromise()
+ */
+void VirtualMachine::promise()
+{
+    impl->promisePending = true;
+    stop();
+}
+
+/*! Resolves the promise so that the VM can continue with the execution. */
+void VirtualMachine::resolvePromise()
+{
+    impl->promisePending = false;
+}
+
 /*! Returns true if the VM has reached the vm::OP_HALT instruction. */
 bool VirtualMachine::atEnd() const
 {